(1) Field of the Invention
The present invention relates to a constant differential pressure valve disposed in a passage of refrigerant circulating through a refrigeration cycle, for controlling the flow rate of the refrigerant according to the amount of an electric current supplied to the valve, such that a differential pressure of the refrigerant across the valve is held constant.
(2) Description of the Related Art
Conventionally, in a refrigeration cycle e.g. for an automotive air conditioner, a high-temperature, high-pressure gaseous refrigerant compressed by a compressor is condensed or cooled by a condenser or a gas cooler, and then the condensed or cooled refrigerant is changed into a low-temperature, low-pressure refrigerant by a decompression device. Further, the low-temperature refrigerant is evaporated by an evaporator, and the evaporated refrigerant is separated into gas and liquid by an accumulator, followed by the separated gaseous refrigerant being returned to the compressor. A decompression device employed in a refrigeration system of the above-mentioned type can be implemented by a constant differential pressure valve that electrically controls the differential pressure of the refrigerant across the valve (see e.g. Japanese Unexamined Patent Publication (Kokai) No. H11-316068).
A constant differential pressure valve of the above-mentioned kind is formed by integrating a differential pressure control mechanism into a body block formed separately from piping constituting a refrigerant passage of a refrigeration cycle, and has separately connected thereto a pipe for introducing a high-pressure refrigerant and a pipe for delivering decompressed refrigerant downstream toward an evaporator, which are separate from each other. An internal valve element is operated by supplying a predetermined electric current to a solenoid, to thereby control the flow rate of refrigerant such that the differential pressure of the refrigerant across the constant differential pressure valve is held constant.
However, this arrangement causes an increase in the size of the entire constant differential pressure valve because the body block is formed separately from the piping of the refrigeration cycle, and further, an internal refrigerant passage where internal structures of the differential pressure control mechanism, such as the valve element, are arranged, and a solenoid section for drivingly controlling the internal structures are disposed in the body block separately from each other. Further, it is necessary to perform complicated adjustment for arranging respective pipes of refrigerant inlet and outlet passages and the internal refrigerant passage connecting the pipes, according to the construction of the differential pressure control mechanism within the body block, which causes an increase in the manufacturing costs of the constant differential pressure valve.